Process for making polynuclear aromatic compounds

ABSTRACT

A process for the production of a polynuclear aromatic compound from an aromatic compound having a labile hydrogen atom attached to its nucleus which involves heating the latter aromatic compound with a noble metal salt of an organic acid in the presence of a strong acid and molecular oxygen in a reaction system free of halide ions and nitrate ions.

United States Patent [191 Selwitz [451 Apr. 17, 1973 [5 PROCESS FORMAKING 3,591,645 7/1971 Selwitz ..260/649 DP POLYNUCLEAR AROMATIC3,636,170 1/1972 Notaro et a]. ....260/649 DP COMPOUNDS 3,644,543 2/1972 Notaro et a1. ....260/649 DP 3,428,700 2/1969 Cyba ..260/668 C [75Inventor: Charles M. Selwitz, Monroeville, Pa. 3,401,207 9/1968 Selwitz1 ..260/670 3,145,237 8/1964 van Helden et al.. ..260/670 [73] Assgnee'Gulf ReFeaRh Devehpmem 3,481,997 12/1969 Vanderwerff ..260/67O pany,Plttsburgh, Pa.

[22] Filed; Nov, 5, 1970 Primary Examiner-Curtis R. Davis 1 pp No:87,289 AttorneyMeyer Nelshloss, Deane E. Keith and References CitedUNITED STATES PATENTS 7/1971 Notaro et al. ..260/649 DP Joseph J.Carducci [57] ABSTRACT free of halide ions and nitrate ions.

12 Claims, No Drawings PROCESS FOR MAKING POLYNUCLEAR AROMATIC COMPOUNDSThis invention relates to a process for producing polynuclear aromaticcompounds whose aromatic nuclei are directly linked to one another bynuclear carbon to nuclear carbon bond, particularly to a process forconverting benzene or substituted benzenes to diphenyl or substituteddiphenyls, respectively.

In my US. Pat. No. 3,401,207, dated Sept. 10, 1968 and assigned to thesame assignee as the present application, I have disclosed and claimed aprocess which comprises treating an aromatic compound with itself orwith another aromatic in a halide-free and a nitratefree system in thepresence of a strong acid catalyst and a noble metal salt of an organicacid, particularly a palladium salt of a carboxylic acid, under selectedconditions and for a time sufficient to obtain polynuclear aromaticcompounds. I have now found that the amount of polynuclear aromaticcompound that can be produced in the process can be appreciablyincreased by carrying out the same in the additional presence ofmolecular oxygen.

Any aromatic compound containing one or more aromatic rings, or amixture of such compounds, having a labile hydrogen attached to at leastone carbon atom in the aromatic nucleus, can be employed herein. Bylabile I mean that the hydrogen possesses an electronic and stericenviromnent which permits its removal from the nucleus. Examples of sucharomatic compounds that can be employed are aromatic compounds havingfrom six to 74 carbon atoms, preferably from six to 24 carbon atoms,such as benzene, toluene, chlorobenzene, methyl benzoate, naphthalene,phenyl acetate, anisole, ortho xylene, cumene,apt-dimethylbenzylsuccinic anhydride, diphenyl, benzoic acid, etc. Thesecompounds when employed herein will form, for example, the followingpolynuclear aromatic compounds: biphenyl, bitolyl, p,p-dichlorobiphenyl,dimethyl biphenyldicarboxylate, binaphthyls, dihydroxybiphenyldiacetate, dimethoxybiphenyl,

The metallic portion of the noble metal salts employed herein ascatalysts include palladium, rhodium, iridium, osmium, ruthenium, andplatinum. Palladium is the preferred metal. The anionic portion of thenoble metal salt can be derived from organic acids, particularlycarboxylic acids, having from one to 40 carbon atoms, preferably fromtwo to 10 carbon atoms, such as formic, acetic, propionic, butyric,pivalic, octanoic, isooctanoic, benzoic, lauric, stearic, isobutyric,paratoluic, gamma-chlorobutyric, tetracontanoic, phenylacetic,cyclohexane carboxylic, crotonic furoic, heptanoic, eicosanoic, etc. Thepreferred carboxylic acid is acetic acid. Examples of such salts thatcan be employed herein include rhodium formate, palladium acetate,palladium propionate, iridium butyrate, palladium pivalate, palladiumoctanoate, osmium isooctanoate, palladium benzoate, palladium laurate,ruthenium stearate, palladium isobutyrate, palladium para-toluate,platinum gammachloro butyrate, ruthenium tetracontanoate, osmiumphenylace-tate, iridium cyclohexane carboxylate, rhodium crotonate,palladium furoate, palladium heptanoate, palladium eicosanoate, etc. Thepreferred salt is palladium acetate.

The cocatalyst employed in the present reaction is a strong acid, thatis, one having an ionization constant K at 25C. of 10' or higher.Specific examples of acids that can thus be employed as catalystsinclude sulfuric, perchloric, phosphoric, trifluoroacetic,glycerophosphoric, iodic, periodic, pyrophosphoric, trichloroacetic,etc.

Preferably the reaction of the present process is carried out in asuitable liquid medium, for example, inert, highly polar compounds.Particularly suitable are carboxylic acids having from one to eightcarbon atoms, preferably from two to five carbon atoms. Examples of suchcarboxylic acids that can be employed include formic, acetic, propionic,butyric, isobutyric, valeric, hexanoic, heptanoic, gamma chlorobutyric,octanoic, methoxyacetic, etc. Acetic acid is preferred. Other liquidsthat can be employed include ethers, amides, sulfoxides, ketones, suchas meta dioxane, dimethylacetamide, dimethylformamide,dimethylsulfoxide, acetone, etc.

The amounts of aromatic compound and catalysts employed herein can bevaried over wide limits. Thus, the mols of noble metal salts relative tothe aromatic compound can be from about 1:6 to about 121000, preferablyfrom about 1:20 to about 1:100. The amount of strong acid relative tothe aromatic compound can be from about 1:3 to about 1:80, preferablyfrom about 1:6 to about 1:12. The amount of liquid medium used need beonly sufficient to facilitate contact among the components therein. Forexample, on a molar basis relative to the aromatic compound the ratioscan be from about 1:1 to about l000:l, preferably within the range ofabout 3:1 to about 50:1. The mols of oxygen provided per mol of aromaticcompound can be from about 2:1 to about 1:20, preferably from about 1:2to about 1:10. Temperatures employed in the reaction can be, forexample, from about 60 to about 200 C., preferably in the range of aboutto about 140 C., and the oxygen pressure can be, for example, from about0.1 to about 1000 pounds per square inch gauge, preferably within therange of about 10 to about 1000 pounds per square inch gauge, mostpreferably from about to about 500 pounds per square inch gauge. Thispressure, with adequate stirring of the contents of the reactionmixture, will assure that sufficient oxygen will be present to obtainthe results desired herein. Reaction time can also vary over a widerange, for example, from about 0.001 to about 100, preferably from about0.1 to about 10 hours.

At the end of the reaction period the desired diphenyls can be recoveredfrom the reaction mixture in any suitable manner. Thus, water can beadded to the reaction mixture. At the bottom of the resultant producethere will be the noble metal, above it a layer containing liquidreaction medium, for example, acetic acid, water and the strong acid,and on top of it diphenyl and unreacted aromatic. The two liquid layerscan be removed therefrom and separated from each other by any suitablemeans, for example, by decantation. The diphenyl can be removed fromexcess, unreacted aromatic compound by any suitable means, for example,

by distillation. The water can be removed from the aqueous layer in anysuitable manner, for example, by distillation, leaving behind the liquidreaction medium and strong acid.

labile hydrogenatom attached to the nucleus thereof which comprisescontacting said latter aromatic compound with a noble metal salt of anorganic acid in the presence of a strong acid and molecular oxygen in aThe process can be further illustrated by the follow- 5 reaction systemfree of halide ions and nitrate ions at a ing, in which two series ofruns were carried out. in one temperature above but below Series therewas place? m a glass flask an ammatfc 2. The process of claim 1 whereinsaid latter arocompound, a strong acid, a noble metal salt and aceticmatic compound is benzene acid. The mixture was refluxed at atmosphericpres- Th f I 1 h l u sure. Refluxing assured that no appreciable amountof lo 1 6 ss s g? 52222:: a er arooxygen was present in the reactionsystem. In the mam: compoun or o c o second series of runs there wasplaced in a heavy glass 4. The process of claim 1 wherein said latteraroflask equipped with a glass stirrer an aromatic commatic compound isorthoxylene. pound, a strong acid, a noble metal salt and acetic acid.5. The process of claim 1 wherein said noble metal The mixture waspressured with oxygen and then Saltis apauadium Salt ofan organic acidbrought to reaction temperature. The pressure was 6 Th f l 1 h M t lmaintained by addition of oxygen during the run. The fi fif 1 g i; no eme a reaction products were analyzed by gas phase chro-. Sa a mms o acarXy cac matography. Data obtained are summarized below in 7. The processof claim 1 wherein said noble metal TABLE 1. salt is palladium acetate.I TABLE I Oxygen pressure.

pounds Mols Oxy- Acetic per per gen, acid, square molof Run Aromat cNoble Milli- Millimlllimilliinch Temp, Time, Compound noble No. compoundGrams metal salt rnols Strong acid mols mols liters gauge C. hoursobtained metal Palladium Dlphenyl- 0. 58 1 Benzene (.7 acetam 5Sulfur1c.. None None 24 {Tgrphenylun 0.12 2 ..do 6.7 do 5 Perchl0rie 10None 100 None 110 24 {g:g;i"" a do 6.7 Palladillm 2.5 Sulfuric... 5 None100 None 110 24 Diphenyl 0.54

. 5 cyan e. 4 Toluene 6.7 Pallatdituni 5 Perchloriu... 10 None 100 None110 24 Ditolyl 0.80

5 Benzene 31.2 do 5 summit... to 64.9 150 170 2'; (s Orthodiehloroso do10 ..d5 10 51. 5 150 a TetrachIoro 14.5

benzene. diphenyl.

7 Orthoxylene 170 do 44.5 do 280 273.0 450 140 120 5,2 Tetramethyl- 6.0

diphenyl.

The data in the above Table clearly show the advantages obtained byoperating in accordance with the procedure disclosed and defined herein.In each of Runs Nos. 1, 2, 3 and 4, wherein the reaction was carried outat atmospheric pressure under reflux with no appreciable amount ofmolecular oxygen in the reaction mixture, a relatively small amount ofdiphenyl was obtained relative to the amount of noble metal salt used.In the remaining runs, however, wherein an oxygen pressure wasmaintained on the reaction system throughout the runs and stirringassured the presence of molecular oxygen throughout the reactionmixture, a significantly larger amount of diphenyls was obtainedrelative to the amount of noble metal salt used.

Obviously, many modifications and variations of the invention, ashereinabove set forth, can be made without departing from the spirit andscope thereof, and therefore only such limitations should be imposed asare indicated in the appended claims.

I claim:

1. A process for the production of a polynuclear aromatic compound froman aromatic compound having a 8. The process of claim 1 wherein saidstrong acid is sulfuric acid.

9. The process of claim 1 wherein the reaction is carried out in aninert liquid medium.

10. The process of claim 1 wherein the reaction is carried out in aceticacid.

11. The process of claim 1 wherein the mols of said noble metal saltrelative to said latter aromatic compound is in the range of about 1:6to about 1:1000, the mols of said strong acid relative to said latteraromatic compound is in the range of about 1:3 to about 12-80, and themols of oxygen per mol of said latter aromatic compoundis in the rangeof about 2:1 to about 1:20.

2. The process of claim 1 wherein said latter aromatic compound isbenzene.
 3. The process of claim 1 wherein said latter aromatic compoundis orthodichlorobenzene.
 4. The process of claim 1 wherein said latteraromatic compound is orthoxylene.
 5. The process of claim 1 wherein saidnoble metal salt is a palladium salt of an organic acid.
 6. The processof claim 1 wherein said noble metal salt is a palladium salt of acarboxylic acid.
 7. The process of claim 1 wherein said noble metal saltis palladium acetate.
 8. The process of claim 1 wherein said strong acidis sulfuric acid.
 9. The process of claim 1 wherein the reaction iscarried out in an inert liquid medium.
 10. The process of claim 1wherein the reaction is carried out in acetic acid.
 11. The process ofclaim 1 wherein the mols of said noble metal salt relative to saidlatter aromatic compound is in the range of about 1:6 to about 1:1000,the mols of said strong acid relative to said latter aromatic compoundis in the range of about 1:3 to about 1:80, and the mols of oxygen permol of said latter aromatic compound is in the range of about 2:1 toabout 1:20.
 12. The process of claim 1 wherein the mols of said noblemetal salt relative to said latter aromatic compound is in the range ofabout 1:20 to about 1:100, the mols of said strong acid relative to saidlatter aromatic compound is in the range of about 1:6 to about 1:12, andthe mols of oxygen per mol of said Latter aromatic compound is in therange of about 1:2 to about 1:10.